DescriptionCumulus Energy Storage is a Rotherham-based developer of grid-scale, long-duration energy storage. Its patented rechargeable copper-zinc battery adapts electrowinning chemistry that the metal-refining industry has run at industrial scale for decades, and uses abundant, recyclable metals, a biodegradable electrolyte and a membrane free of forever chemicals. The technology is designed for 4 to 24 hour charge and discharge cycles, with applications in renewable time-shifting, electricity network constraint management, private-wire microgrids, electrification of mining and metal processing, and low-cost green hydrogen. Cumulus is moving from demonstration towards pilot-line production, with operations in the UK, the United States and Germany.